When calves arrive in feedyards managers, crews and veterinarians have better vaccines, better treatments and more information on bovine respiratory disease (BRD) than ever before. And yet, BRD persists as the most economically damaging disease in beef production.

Increasingly, cattle feeders and veterinarians recognize the relationship between stress and immunity. Weaning, commingling, shipping, processing and introducing calves to the feedyard environment all contribute to stress, suppression of immunity and limited response to vaccinations.

However, based on convenience, tradition and a perception of urgency, feedyards often vaccinate calves with modified-live virus (MLV) vaccines upon arrival or soon after.

Texas A&M University animal scientist John Richeson studies stress-induced immunosuppression in cattle—particularly vaccine response. He points to the difference between vaccine efficacy and efficiency. A strong antibody titer response suggests vaccine efficiency.  Vaccine efficiency refers to reduced instances of morbidity and mortality and improved performance. So, a vaccine could be eefficacious but not efficient due to factors like chronic stress.

Richeson notes some studies comparing MLV vaccinations delayed for 14 days versus vaccination upon arrival have shown reductions in BRD, while other studies have found no difference.

Testing the theory turned competitors to collaborators.

In an unusual research project, two competing animal health companies, Boehringer Ingelheim Vetmedica, Inc., (BIVI) and Bayer Animal Health, collaborated to explore the effects of a 30-day delay in administering a MLV vaccine, along with using an immunostimulant in high-risk calves.

The research project explored the effects of delayed respiratory MLV viral vaccine (Pyramid 5) with or without the inclusion of an immunostimulant (Zelnate) on feedlot health, performance and carcass merits of auction-market-derived feeder heifers. Del Miles, DVM, Veterinary Research and Consulting Services in Greeley, Colo., managed the trial.

A total of 5,179 high-risk heifer calves in 60 pens, were divided into four treatment groups of 15 pens The treatments included:

·       Delayed vaccine at 30 days

·       Vaccine on arrival and at 30 days

·       Immunostimulant on arrival and delayed vaccine at 30 days

·       Immunostimulant and vaccine on arrival and revaccination at 30 days.

The arrival protocol for all the animals included Mannheimia haemolytica toxoid, tilmicosin, moxidectin, oxfendazole and determination of pregnancy status.

The MLV used in this trial contains antigens against infectious bovine rhinotracheitis virus (IBRV), parainfluenza-3 virus (PI3V), bovine viral diarrhea virus types 1 and 2 (BVDV) and bovine respiratory syncytial virus (BRSV). The researchers administered 2mL of the vaccine subcutaneously in the right neck. As per label instructions, the researchers administered the 2mL of the DNA immunostimulant intramuscularly in the left neck.

Health outcomes showed a delay of MLV improved results.

At 60 days on feed, covering a period that typically brings the highest incidence of respiratory disease, the researchers found no significant differences between the treatment groups in the incidence of cattle treated once for respiratory disease. However, the delayed vaccination groups, with or without the immunostimulant, had a significantly lower percentage of calves treated twice.

As for the immunostimulant treatment, the researchers observed no significant difference in the percentage of calves treated once or twice for BRD during the first 60 days on feed, but they did see a reduction in third treatments. Notably, they found a significant reduction in the percentage of BRD mortality and overall mortality in the immunostimulant groups, suggesting the product positively influenced the survivability of those calves that were treated for respiratory disease.

The researchers noted similar results at 116 days on feed and at closeout.

Through the feeding period, 25.8% of the heifers were treated for BRD and 10.6% were treated more than once. Average retreatment risk for the delayed-vaccination groups was 37.05%, compared with 43.97% for the heifers vaccinated upon arrival.

At closeout, average overall mortality was 4.36% in groups that received the immunostimulant versus 5.61% for those that did not. BRD mortality followed a similar trend, averaging 2.99% in treated groups versus 3.96% in groups that did not receive the immunostimulant.

In this study, the researchers concluded delaying the MLV vaccine for 30 days resulted in a significant decrease in the number of calves requiring additional treatment for BRD. Also, the inclusion of a DNA immunostimulant “consistently improved survivability as evidenced by a significant reduction in total mortality at 60 days, 116 days and closeout, resulting in a 22% reduction in overall death loss.”

One underlying factor in this work is animal-health outcomes have not improved in recent years, in spite of advancements in technology and cattle management, says Jerry Woodruff, DVM, BIVI technical services veterinarian and one of the authors of the research report.

Transition to the feedyard “is a whole new world for calves,” Woodruff says, noting stress likely impacts the immune status of medium-risk cattle as well as high-risk cattle.

Delayed vaccination represents a paradigm shift for cattle feeders, who typically vaccinate new arrivals as soon as possible, he adds. Researchers in this trial did not eliminate all preventative disease measures at arrival, which included a bacterin against bacterial pneumonia and mass medication for BRD prevention.

Practice mirrors research results.

Even before the trial was complete, feedyard veterinarian Del Miles, who helped execute the study, put the procedure into practice at other feedyards. He begins delaying use of the MLV respiratory vaccination in high-risk cattle for 30 days after arrival.

Practical experience, he says, has matched the results of the study. He uses the immunostimulant in high-risk calves and again has seen results similar to those from the study.

In low-risk yearlings, he continues to vaccinate upon arrival to avoid an additional trip through the processing area. Also, when ranch calves arrive with documentation they have received a five-way MLV viral vaccine within the past six months, he doesn’t repeat the vaccination on arrival.

In most cases, his feedyard clients who delay vaccinations in high-risk calves use processing protocols similar to that in the study, including a Mannheimia haemolytica toxoid, deworming and external parasite control as needed.

 

Note: This story appears in the February 2017 issue of Drovers.